QEMU window does no open on Ubuntu 21.04 when Test button is clicked.

This issue occurs because qemu-system-gui is not installed. In addition to Kubuntu, this also affects Ubuntu.

Even in Ubuntu 21.04, the qemu-system-gui package is not installed when qemu-system-x86 is installed using the no-install-recommends option. Note that it is recommended to install Cubic using sudo apt install --no-install-recommends cubic.

$ sudo apt install --no-install-recommends qemu-system-x86
The following additional packages will be installed:
  ipxe-qemu ipxe-qemu-256k-compat-efi-roms libcacard0 libdaxctl1 libfdt1
  libibverbs1 libiscsi7 libndctl6 libpmem1 librados2 librbd1 librdmacm1
  libslirp0 libspice-server1 liburing1 libusbredirparser1 libvirglrenderer1
  qemu-block-extra qemu-system-common qemu-system-data seabios
Suggested packages:
  gstreamer1.0-libav gstreamer1.0-plugins-ugly samba vde2
Recommended packages:
  ibverbs-providers qemu-system-gui qemu-utils ovmf cpu-checker
The following NEW packages will be installed:
  ipxe-qemu ipxe-qemu-256k-compat-efi-roms libcacard0 libdaxctl1 libfdt1
  libibverbs1 libiscsi7 libndctl6 libpmem1 librados2 librbd1 librdmacm1
  libslirp0 libspice-server1 liburing1 libusbredirparser1 libvirglrenderer1
  qemu-block-extra qemu-system-common qemu-system-data qemu-system-x86 seabios

Proposed fix released to experimental branch, revision 21.

https://bazaar.launchpad.net/~cubic-wizard/cubic/experimental/revision/21

After testing, the fix did not work.

Require qemu-system-x86 for all Ubuntu versions. Only require qemu-system-gui for Ubuntu versions > 18.04 Bionic. (qemu-system-gui is not available for Ubuntu 18.04 Bionic, but it is not required for Zoom to Fit).

Ubuntu 18.04 Bionic:
- Install qemu-system-x86 1:2.11
- qemu-system-gui is not available

Ubuntu 20.04 Focal:
- Install qemu-system-x86 1:4.2
- Install qemu-system-gui 1:4.2; does not depend on qemu-system-x86

Ubuntu 20.10 Groovy (unsupported, so there is no Cubic build for 20.10)
- Install qemu-system-x86 1:5.0
- Install qemu-system-gui 1:5.0; does not depend on qemu-system-x86

Ubuntu 21.04 Hirsute:
- Install qemu-system-x86 1:5.2
- Install qemu-system-gui 1:5.2; depends on qemu-system-x86

Ubuntu 21.10 Impish:
- Install qemu-system-x86 1:6.0
- Install qemu-system-gui 1:6.0; depends on qemu-system-x86

Proposed fix released to experimental branch, revision 28.

https://bazaar.launchpad.net/~cubic-wizard/cubic/experimental/revision/28

After testing, the fix worked on

  1. Ubuntu 18.04 Bionic
  2. Kubuntu 18.04 Bionic
  3. Ubuntu 20.04 Focal
  4. Ubuntu 21.04 Hirsute
  5. Ubuntu 21.10 Impish

The fix will be applied to release branch, revision 58.

Fix released in version 2021.10-58.